Numerous acoustic instruments are used to map the seafloor’s surface and underlying geology. 

• Differential GPS provides navigation for the ship and equipment.
• An echosounder measures water depth directly beneath the vessel.  
• Swath bathymetry, which includes multibeam and interferometric sonars, improves efficiency by simultaneously measuring water depth and the intensity of sound reflected from the seafloor in a swath to either side of the vessel. 
• Seismic-reflection systems explore the layers of sediment beneath the seafloor by measuring the intensity of sound reflected from the seafloor and underlying layers. 
• Sidescan-sonar produces the marine equivalent of an aerial photograph by measuring the intensity of sound reflected from the seafloor in a swath to either side of a towed vehicle. 
• After acoustically mapping the seafloor’s surface and underlying geology, sediment samples, bottom photographs and/or video must be collected from the seafloor in order to groundtruth, or validate, the acoustics.

Credit: U.S. Geological Survey